1. Field of the Invention
The present invention is about a new technology for self-cooling food and beverage containers and about methods of manufacturing these containers. The novel invention is a simple and cost effective apparatus and the invention reveals a new way of manufacturing and using this apparatus to store high pressure refrigerants such as CO2, CF4, nitrogen and Co2 mixtures and other suitable gases. The technology can be described as a graded pressure index technology. The terms used in this description of the invention can take on several meaning all of which are related to the subject matter. For example the terms “food” and “beverage” are interchangeable. One skilled in the art will appreciate that the use of general terms does not hamper the inventiveness.
2. Description of the Prior Art
Many self-cooling beverage systems have been described in prior art. In particular, systems that use rigid containers or flexible receptacles have been described. However, all these systems lack the inventiveness of the present invention. All prior art relies on a continuous and even pressure distribution in either a single-walled container, or a series of containers, and they all fail to apply a graded pressure support technology to hold high pressure refrigerants. The real problem in using a low cost flexible member in such applications, stems from the fact that a simple receptacle built from flexible plastic materials cannot hold the pressure of such refrigerants because the hoop and lateral stresses break the walls easily, and one cannot easily rely on making the walls thicker, since the walls themselves are subject to limiting stresses no matter how thick one makes them. Further, one loses the commercial viability by using thick-walled containers that can be very cost prohibitive.
U.S. Pat. Nos. 5,704,222 and 5,946,930 to Anthony shows a flexible receptacle that relies on pressure equilibration across the walls of the receptacle. Thus, in these inventions Anthony describes how a low cost flexible plastic receptacle can be used to store a high pressure fluid by transmitting the pressure of a beverage through the receptacle walls and equilibration of the pressure inside the refrigerant receptacle with the pressure outside the receptacle.
In all these prior inventions, the receptacle walls are in perfect equilibrium, holding no pressure forces, since the pressure forces acting on each side of the receptacle is the same. Suffice it to say that the inventiveness of these flexible receptacles is based on inventions by Anthony are indeed innovative, but they are limited as follows:                a) the Anthony receptacles have equal pressures on the inside and outside walls of the receptacle, and so do not experience any forces.        b) the Anthony receptacles rely on the beverage container to ultimately hold the refrigerant pressure.        
It is one of the objectives of the present invention to disclose a new method of graded pressure indexing to gradually transmit pressure forces through a series of concentric flexible receptacles from a high pressure region in the inner most receptacle to a low pressure region in the outermost receptacle, so that the gradual graded index pressure gradient is insufficient to destroy each of the receptacles. It is then important that for the practice of the present invent, none of the receptacles maintain a pressure differential across its walls that can destroy it. Suffice it to say that the seemingly impossible can be achieved by a gradual pressure gradient, such that each pressure differential is below the pressure holding capacity of each nested receptacle member. So, with great pride, I declare that such a combination of receptacles can ultimately hold a very high pressure within them; the differential across each wall is small enough to be held completely by the receptacle wall in question. It is therefore a precious advantage of the present invention that each pressure receptacle is capable of holding across its walls some pressure differential without being destroyed.
It is a further great advantage of this invention that this high pressure flexible receptacle that can be easily inserted to a beverage bottle or beverage metal can because it is flexible. Thus, pressure equilibration is undesirable for this invention, since if all the nested receptacles were to equilibrate the pressure differentials across their walls, the ultimate high pressure within the inner most receptacle will indeed be transmitted to the outer most receptacle and the receptacles will successive be destroyed by this high pressure. The Anthony inventions are therefore inadequate to perform the functions of holding pressures beyond the capacity of the beverage container itself.